1. Field of the Invention
The present invention relates to wireless communications, and more specifically to a method and apparatus for selecting one of multiple antennas to receive signals in a wireless packet network.
2. Related Art
Data packets are often transmitted using wireless technologies. For example, a stream of bits representing voice may be transmitted in the form of packets using standards such as CDMA. In general, a packet contains a payload portion representing the data of interest to be transported, and a non-payload portion (containing subportions such as preamble, postamble, midamble, training sequences).
A typical sending system transmits each packet in several directions (angles). Each transmitted signal may be bounced (reflected) by several surfaces present in a corresponding path before reaching a receiving system. Before reaching the receiving system, each reflected signal may undergo different degrees of attenuation, phase rotations and be subject to different noise levels depending on various factors as is well known in the relevant arts.
A receiving system may employ multiple antennas to receive packets. In general, multiple antennas are employed such that at least one of the antennas is located in a path of a signal which is more conducive (e.g., high strength/amplitude) for the recovery of the encoded data, and it is generally desirable that the signal received by such an antenna (in the path of the strong signal) be examined to recover the encoded bits of the packet.
In situations where only two antennas are used, the two antennas may be separated by a distance of λ/2, wherein λ represents the wavelength corresponding to frequency of operation of the communication system. Accordingly, there is a general need to select one among multiple antennas when receiving a packet using wireless technologies.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.